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><DIV
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><H1
><A
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></A
>Chapter 42. PL/Python - Python Procedural Language</H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
>42.1. <A
HREF="plpython-python23.html"
>Python 2 vs. Python 3</A
></DT
><DT
>42.2. <A
HREF="plpython-funcs.html"
>PL/Python Functions</A
></DT
><DT
>42.3. <A
HREF="plpython-data.html"
>Data Values</A
></DT
><DD
><DL
><DT
>42.3.1. <A
HREF="plpython-data.html#AEN56673"
>Data Type Mapping</A
></DT
><DT
>42.3.2. <A
HREF="plpython-data.html#AEN56723"
>Null, None</A
></DT
><DT
>42.3.3. <A
HREF="plpython-data.html#PLPYTHON-ARRAYS"
>Arrays, Lists</A
></DT
><DT
>42.3.4. <A
HREF="plpython-data.html#AEN56741"
>Composite Types</A
></DT
><DT
>42.3.5. <A
HREF="plpython-data.html#AEN56770"
>Set-returning Functions</A
></DT
></DL
></DD
><DT
>42.4. <A
HREF="plpython-sharing.html"
>Sharing Data</A
></DT
><DT
>42.5. <A
HREF="plpython-do.html"
>Anonymous Code Blocks</A
></DT
><DT
>42.6. <A
HREF="plpython-trigger.html"
>Trigger Functions</A
></DT
><DT
>42.7. <A
HREF="plpython-database.html"
>Database Access</A
></DT
><DD
><DL
><DT
>42.7.1. <A
HREF="plpython-database.html#AEN56907"
>Database Access Functions</A
></DT
><DT
>42.7.2. <A
HREF="plpython-database.html#PLPYTHON-TRAPPING"
>Trapping Errors</A
></DT
></DL
></DD
><DT
>42.8. <A
HREF="plpython-subtransaction.html"
>Explicit Subtransactions</A
></DT
><DD
><DL
><DT
>42.8.1. <A
HREF="plpython-subtransaction.html#AEN56973"
>Subtransaction Context Managers</A
></DT
><DT
>42.8.2. <A
HREF="plpython-subtransaction.html#AEN56988"
>Older Python Versions</A
></DT
></DL
></DD
><DT
>42.9. <A
HREF="plpython-util.html"
>Utility Functions</A
></DT
><DT
>42.10. <A
HREF="plpython-envar.html"
>Environment Variables</A
></DT
></DL
></DIV
><P
>  The <SPAN
CLASS="APPLICATION"
>PL/Python</SPAN
> procedural language allows
  <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> functions to be written in the
  <A
HREF="http://www.python.org"
TARGET="_top"
>Python language</A
>.
 </P
><P
>  To install PL/Python in a particular database, use
  <TT
CLASS="LITERAL"
>CREATE EXTENSION plpythonu</TT
>, or from the shell command line use
  <TT
CLASS="LITERAL"
>createlang plpythonu <TT
CLASS="REPLACEABLE"
><I
>dbname</I
></TT
></TT
> (but
  see also <A
HREF="plpython-python23.html"
>Section 42.1</A
>).
 </P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
>    If a language is installed into <TT
CLASS="LITERAL"
>template1</TT
>, all subsequently
    created databases will have the language installed automatically.
   </P
></BLOCKQUOTE
></DIV
><P
>  As of <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> 7.4, PL/Python is only
  available as an <SPAN
CLASS="QUOTE"
>"untrusted"</SPAN
> language, meaning it does not
  offer any way of restricting what users can do in it.  It has
  therefore been renamed to <TT
CLASS="LITERAL"
>plpythonu</TT
>.  The trusted
  variant <TT
CLASS="LITERAL"
>plpython</TT
> might become available again in future,
  if a new secure execution mechanism is developed in Python.  The
  writer of a function in untrusted PL/Python must take care that the
  function cannot be used to do anything unwanted, since it will be
  able to do anything that could be done by a user logged in as the
  database administrator.  Only superusers can create functions in
  untrusted languages such as <TT
CLASS="LITERAL"
>plpythonu</TT
>.
 </P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>   Users of source packages must specially enable the build of
   PL/Python during the installation process.  (Refer to the
   installation instructions for more information.)  Users of binary
   packages might find PL/Python in a separate subpackage.
  </P
></BLOCKQUOTE
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